1. Technical Field
The present invention relates to liquid ejecting heads, liquid ejecting head units, and liquid ejecting apparatuses that eject liquid from nozzles.
2. Related Art
Liquid ejecting heads that eject liquid droplets from a nozzle by applying pressure to the liquid, using a piezoelectric element, have been known for some time. Ink jet recording heads that eject ink droplets from the nozzles are one example.
A typical ink jet recording head includes multiple pressure generation chambers at one surface of a nozzle plate in which multiple nozzles are provided, each of the pressure generation chambers communicating with respective nozzles. An ink chamber or manifold provides the ink to the pressure generation chambers. A piezoelectric element forces ink out of the nozzles by causing the pressure within the pressure generation chambers to change. A cavity faces each manifold to absorb pressure fluctuations in the liquid within the common manifold. An example of such a recording head is disclosed in Japanese Patent Publication 2005-289074, published on Oct. 20, 2005, the contents of which are hereby incorporated by reference.
The cavity is open to the air to keep the pressure within it constant. There are thus situations where the water content within the ink evaporates from the cavity and causes a rise in the viscosity of the ink, which leads to ejection problems. Accordingly, excessive evaporation is prevented by a control channel offering channel resistance that prevents evaporation.
However, with the demand for an increase in the viscosity of inks, the maintenance of favorable ink ejection properties over a long period of time, and so on, there is now more than ever a further demand to prevent evaporation.
This problem exists not only for ink jet recording heads, but for any liquid ejecting head that ejects a liquid.